[英]Reverse a string using a recursive function
I am currently studying C and I can't get past this exercise. 我目前正在学习C,我无法通过这项练习。 I must create a recursive function to reverse string1
into string2
. 我必须创建一个递归函数来将string1
反转为string2
。 Here is my code. 这是我的代码。 I would gladly appreciate your help. 我很乐意感谢你的帮助。
#include <stdio.h>
#define MAX 100
void reverse(char s1[],char s2[],int n,int j);
int main()
{
char string1[MAX]="How Are You Mate";
char string2[MAX]="";
int n=0;
int i=0;
int j=0;
for(i=0;string1[i]!='\0';i++)
n++;
reverse(string1,string2,n,j);
printf("String-a normal:\n%s\n",string1);
printf("String-a reverse:\n%s\n",string2);
return 0;
}
void reverse(char s1[],char s2[],int n,int j)
{
if(n>0)
{
s2[j]=s1[n];
reverse(s1,s2,n-1,j+1);
}
else
s2[j]='\0';
}
in-place (the caller could make a copy of the string before calling this function) string reverse with tail-recursion 就地(调用者可以在调用此函数之前复制字符串)字符串反向使用尾递归
void reverse (char *str, size_t len)
{
char tmp;
if (len-- < 2) return;
tmp = *str;
*str = str[len];
str[len] = tmp;
reverse (str+1, len -1);
}
O, if you don't want pointers: 哦,如果你不想要指针:
void reverse (char str[], size_t len)
{
char tmp;
if (len-- < 2) return;
tmp = str[0];
str[0] = str[len];
str[len] = tmp;
reverse (str+1, len -1);
}
The reversing starts by copying the n
-th character of string1
array into string2
. 通过将string1
数组的第n
个字符复制到string2
开始反转。 The n
-th character happens to be the null terminator. 第n
个字符恰好是空终止符。 It becomes the first character of your new string, so the string looks empty to all standard C routines, including printf
. 它成为新字符串的第一个字符,因此字符串对于所有标准C例程(包括printf
看起来都是空的。
Calling 调用
reverse(string1,string2,n-1,j);
from the main
should fix the problem. 从main
应该解决问题。 The condition in the reverse
should be changed from if(n>0)
to if(n>=0)
as well. reverse
条件也应该从if(n>0)
变为if(n>=0)
。
Although it does not save the resulting string anywhere, you get the idea. 虽然它不会将结果字符串保存在任何地方,但您可以理解。
#include <stdio.h>
void rev (const char* str);
int main () {
const char str[] = "!dlrow ,olleH";
printf("%s\n", str);
rev(str);
printf("\n");
return 0;
}
void rev (const char* str) {
char c = *str;
if (c != '\0') {
rev(str + 1);
printf("%c", c);
}
}
I have corrected the program. 我已经纠正了这个程序。 Please find the changes below 请在下面找到更改
void reverse(char s1[],char s2[],int n,int j)
{
if(n>0)
{
s2[j]=s1[n-1];
reverse(s1,s2,--n,++j);
}
else
s2[j]='\0';
}
i recommend using library , size=strlen(array) in stead of 我建议使用library,size = strlen(array)来代替
for(i=0;string1[i]!='\0';i++)
n++;
to count how many characters in arra 计算arra中有多少个字符
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